There is a powerful reason President Vladimir Putin won't win Bashar al-Assad's war for him. As with Russia's limited military participation in the conflict in eastern Ukraine, Putin doesn't want casualties, because not even his powerful propaganda machine can conceal them.

On Tuesday, Russia acknowledged its first military casualty in Syria: Vadim Kostenko, a 19-year-old air force technician. The Defense Ministry, which flatly denied all previous reports of casualties, didn't volunteer the information. Instead, the Conflict Intelligence Team, a volunteer group run by the blogger Ruslan Leviev that scours social networks to track Russian military activity, discovered that Kostenko died Oct. 24.

Leviev's team used the same approach it has to track the Russian army's presence in Ukraine and the death toll there: It combed the social network for accounts of soldiers from units believed or reported to be involved in the action, and those of their friends. After discovering an epitaph for Kostenko, the team contacted his relatives and friends to confirm the death and discovered that a representative of Kostenko's unit had told his family that he had killed himself.

The Defense Ministry said Tuesday that data on Kostenko's mobile phone suggested he had a falling out with his girlfriend. Kostenko's parents and sister didn't believe it, though. They said he had been cheerful when he talked to them on the day he died and that he and his girlfriend had been doing great and been planning to get married.

The Defense Ministry's initial silence and the shaky suicide narrative indicate that Russian military officials are reluctant to recognize any deaths.

The Syrian operation was supposed to be low-cost. And in some ways, it is. Last week, The Moscow Times collaborated with the research group IHS Jane's to come up with an estimate of the cost of the intervention. It said Russia was spending about $710,000 a day on aircraft sorties, $750,000 on munitions, $440,000 to support its personnel in Syria, $200,000 to maintain its naval presence and $250,000 on logistics, intelligence and communications. The total could be as much as $4 million a day. It's a tiny amount compared with Russia's $50 billion defense budget. A year of warfare at this rate would cost about as much as the $1.25 billion spent on government-controlled media this year, and the propaganda benefits are probably greater.

The cost in human lives, though, is a different matter. Levada Center, one of Russia's few remaining independent polling services, said that in early October, immediately after the Syria operation began, 72 percent of Russians supported the idea of bombing raids against the so-called Islamic State. Yet 46 percent were worried that Russia could get bogged down in Syria, as it did in Afghanistan in the 1980s.

Putin is authoritarian, but mindful of public opinion. He justifies his rule with the more than 80 percent support he enjoys in polls. Given Russia's precarious economic situation -- the price of oil is below the comfort level -- signs of an Afghanistan-style disaster could easily erode that support.

During the Ukraine campaign, the Kremlin's tactic was to meet any mention of casualties with deafening denials: Russia has never admitted that it had any regular troops in eastern Ukraine, so no soldiers were killed. This largely worked because the casualties were in the dozens or, at worst, hundreds. Families could be silenced with threats and promises, social network accounts deleted, fresh graves explained away.

With Syria, though, hiding even a small number of casualties is impossible. Russia is officially involved, and it would be unacceptable to fail to honor the killed in action.

More stories about suicides wouldn't be sustainable, either.

The troops who fought in Afghanistan were draftees. Those in Syria are professionals, but that won't make their families grieve any less or improve public attitudes toward the Middle Eastern adventure.

Putin has vehemently denied any plans to deploy ground troops in Syria. Although his handling of Ukraine has thoroughly devalued such denials, he may mean it this time.

This is bad news for Assad. His ground offensive, backed by the Russian airstrikes, has been slow and not particularly successful. Islamic State fighters appear to be pushing back near Aleppo. If the Syrian army is stopped, there's little chance Russia would come to the rescue as it did at decisive moments in eastern Ukraine. Russia could mount an operation that it could deny, as it did in Ukraine, but Assad cannot count on that. He needs a victory on the ground to ensure continued Russian support.

The Kremlin has made that clear by offering help to some of Assad's opponents as they battle Islamic State. If Assad fails to deliver, Putin might let him go and negotiate his downfall with the U.S.-led coalition. According to the Levada Center, 49 percent of Russians believe Moscow will make a deal with the West. Putin has more to gain by meeting these expectations than he would by getting bogged down in what could look like Afghanistan-2.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.